In a scientific review paper published online on January 28, 2016 in the peer-reviewed journal Trends in Food Science & Technology, Hoppe and colleagues from the Fraunhofer Institute for Process Engineering and Packaging IVV, Germany provide a comprehensive overview of oligomers potentially migrating from polymeric food contact materials (FCMs), covering their formation pathways, analytical methods and migration data.

Oligomers consist of 2 to 40 monomeric units and can be linear, branched or cyclic. They are formed as a result of either incomplete polymerization or subsequent degradation (thermal or hydrolytic) of polymeric material. The variety of possible oligomers constantly increases with the introduction of novel monomers and monomer combinations on the FCM market. Such a diversity, accompanied by the dearth of appropriate analytical standards, makes both qualitative and quantitative characterization of oligomeric migrants, as well as evaluation of their toxicity, a challenging task.

Detection, identification and quantification of oligomers are best accomplished by liquid chromatography coupled with mass spectrometry (LC-MS) approaches. To ease identification, theoretical oligomer masses can be calculated from known monomer units. Safety assessment for oligomers has been traditionally based on the respective monomers, since physiological degradation of oligomers to monomers is assumed. However, polycondensate type cyclic oligomers may need to be considered separately; their susceptibility to hydrolysis in the gastrointestinal tract and their toxic properties are incompletely understood so far.

Up to now, the tendency has been to consider oligomers within the broad group of non-intentionally added substances (NIAS). However, since oligomer chemistry is determined by a polymer manufacturing process, the authors suggest to consider oligomers as a separate group of polymer-specific substances. This is also supported by analytical and toxicological considerations, since homologue series of oligomers tend to have similar properties and thus can be analyzed and evaluated by the same approaches.

Reference

Hoppe, M. et al. (2016). “Identification and quantification of oligomers as potential migrants in plastics food contact materials with a focus on polycondensates – A review .Trends in Food Science and Technology 50:118-130.

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